The under construction Burj Dubai in Dubai, United Arab Emirates is the world’s current tallest freestanding structure on land, rising 604.9 m (1,985 ft). When completed, it is planned to rise over 800 m (2,625 ft).
The CN Tower in Toronto, Ontario was the world’s tallest freestanding structure on land from 1975 until the Burj Dubai surpassed it in 2007, rising 553.33 m (1,815 ft). It is currently the world’s tallest completed freestanding structure on land.
http://en.wikipedia.org/wiki/List_of_tallest_buildings_and_structures_in_the_world
Top 20 Under Construction
1 Burj Dubai
As of 24 October 2007, Burj Dubai’s official website reported its height to be 585.7 m (1,922 ft), with 156 completed stories.
http://www.tallestbuildingintheworld.com/building_id_106_Burj+Dubai.php
Top 20
With a massive 60-foot spire inspired by Twaiwan’s native bamboo plant, Taipei 101 Tower is one of the tallest buildings in the world. At 508 meters (1,667 feet) high, the tower and its spire outrank the Petronas Twin Towers in Kuala Lumpur, Malaysia. Taipei Tower has 198,347 m2 (2,336,000 sq. ft.) of office space, 77,033 m2 (796,000 sq. ft.) of retail space, and 83,000 m2 (893,000 sq. ft.) of parking space for more than 1,800 vehicles.
http://www.tallestbuildingintheworld.com/building_id_2_Taipei+101.php